a) Field of the Invention
The invention relates to a steering column for a motor vehicle, which is adjustable at least in its longitudinal direction, comprising a support unit connectable with the chassis of the motor vehicle, a setting unit disposed between the side jaws of the support unit, and a clamping mechanism. In the opened state of the clamping mechanism, the setting unit is displaceable with respect to the support unit at least in the longitudinal direction of the steering column and, in the closed state of the clamping mechanism, the set position of the setting unit with respect to the support unit is secured in position. The clamping mechanism comprises a clamp bolt which penetrates openings in the side jaws of the support unit, and during the opening and closing of the clamping mechanism is rotated about its axis. At least one securement part is provided between the side jaws of the support unit and displaced through the rotation of the clamp bolt during the opening and closing of the clamping mechanism, which in the closed state of the clamping mechanism engages into a counter-securement part connected with the setting unit, or at least during the dislocation beginning in the event of a motor vehicle crash of the setting unit with respect to the support unit comes into engagement with the counter-securement part and which, in the opened state of the clamping mechanism, is spaced apart from the counter-securement part.
b) Description of Related Prior Art
Adjustable steering columns serve to adjust the position of the steering wheel to the seating position of the driver and are known in various embodiments. Apart from adjustable steering columns which are only adjustable in length or height and inclination direction, respectively, steering columns are known which are adjustable in length as well as also height and inclination direction, respectively. Such adjustable steering column is, for example, disclosed in EP 0 802 104 A1. In the opened state of the clamping mechanism, a setting unit, pivotably supporting the steering spindle, is, with respect to a chassis-stationary support unit, displaceable in the direction of a length adjustment as well as also in the direction of a height or inclination adjustment of the steering column. To increase the holding forces in the closed state of the clamping mechanism, the clamping mechanism comprises intersecting (lamella) disk packs cooperating in the manner of a lamella coupling.
Several arrangements have already been proposed for adjustable steering columns to provide, in the event of a crash of the motor vehicle, an additional holding force against a dislocation of the setting unit with respect to the support unit in order to prevent the unchecked displacement of the steering column whereby, under control through an energy absorption device of the steering column, energy absorption is also made possible. Such an energy absorption device is configured such that, for example, the support unit is realized in the manner of a carriage which is shiftably supported on a chassis unit rigidly disposed on the motor vehicle chassis, wherein between the chassis unit and the support unit an energy absorption device, for example a flexural strip, is formed.
Such an implementation is disclosed in WO2006042604. An adjustable steering column is introduced here, in which for the energy consumption during the dislocation of the holding part which pivotably supports the steering spindle, with respect to the support panel secured on the motor vehicle, a flexural plate bent in the shape of a U is provided which, in the event of a crash, effects the energy absorption by bending and through the additional tearing-open along notchings provided for this purpose. In order for the energy absorption to take place, in fact, via these notchings, it is, however, necessary to ensure that the adjustable steering column does not become dislocated within the scope of the possible adjustment range. For this purpose, the securement device with which the desired position is arrested after an adjustment must be appropriately laid out. According to WO2006042604, an additional crash blocking device is provided for this purpose. A clamping wedge is provided which, in the event of a crash, is slid into a gap between the setting unit and the support unit. The clamping wedge is connected with the clamp bolt or with a part jointly moved axially together. During the closing of the clamping mechanism, this is axially shifted together with the clamp bolt such that a contact face of the clamping wedge comes into contact on a contact face of the setting unit in order for the clamping wedge in the event of a crash during the onsetting dislocation of the setting unit to be entrained by the latter.
DE 10 2005 052 123 B3 further discloses an energy absorption device for the absorption of energy in the event of a crash, in which an arrest element disposed on the setting unit with which, in the closed state of the securement device serving for the securement of the set position of the steering column, a counter-arrest element is in engagement is so connected that in the event of a crash it is shiftable with the absorption of energy in the longitudinal direction of the steering column with respect to the setting unit. A further arrest element of a securement device shiftable with respect to the setting unit with the absorption of energy is disclosed in EP 1 464 560 A2.
U.S. Pat. No. 6,139,057 A discloses an adjustable steering column of the type described in the introduction. On the clamp bolt is disposed a securement part which, through the rotation of the clamp bolt, is turned during the opening and closing of the clamping mechanism, wherein a spring-elastic element acts between the clamp bolt and the securement part. In the closed state of the clamping mechanism, a toothing of the securement part engages into a toothing of a counter-securement part which is formed by a frame welded onto the inside of a side jaw of the setting unit. In the opened state of the clamping mechanism the toothing of the securement part is raised off the toothing of the counter-securement part. Through this arrangement, an additional holding force is applied against a longitudinal displacement of the steering column in the event of a motor vehicle crash. An arrangement is provided acting analogously in the event of a crash against the displacement of the height or inclination setting. Through the arrangement disclosed in this publication the requisite installation space of the steering column is enlarged and the tooth widths of the cooperating toothings can only be implemented such that they are relatively small whereby the additional holding force of the crash blocking arrangement is limited.
US 2006/009 0586 A1 discloses a similarly acting crash holding arrangement which acts only against a displacement of the steering column in the height or inclination direction.